A Low Frequency Oscillator(LFO) generates a carrier signal that can be used to modulate a control on a synthesiser. Typically LFO's are used to modulate pitch and amplitude; however they can be very effective of all manner of controls including filter cutoff, resonance, pulse width and panning.

The below diagram demonstrates the effect of an LFO carrier signal when used to modulate the Pitch and Amplitude of a signal:

There are two common controls associated with an LFO, these are Speed and Depth.

Speed
Low Frequency Oscillators usually generate frequencies from 0.01 Hz up to 40Hz..
If you wish to synchronize the rate of the LFO to the song tempo, you can simply use the formula:

Depth
The depth control sets the amount of effect that the LFO carrier has upon the destination (e.g. pitch) generally the depth control is not found on the LFO but upon the device you wish to modulate (e.g. the main oscillator)

Wave shape
Many LFO devices allow you to select the waveform of the LFO modulation, these are typically the same as a normal oscillator i.e. sine, triangle, square, saw tooth, random.

Keyboard tracking
Some LFO's may feature a keyboard tracking level, this links the speed of modulation to the note pitch on the keyboard and can be used for some interesting effects.

© Nathan Boddy 2006 unauthorised copying or duplication prohibited.

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